Featured Research

from universities, journals, and other organizations

Highly unidirectional 'whispering gallery' microlasers created

Date:
December 13, 2010
Source:
Harvard University
Summary:
Utilizing a century-old phenomenon discovered in St. Paul's Cathedral, London, scientists have demonstrated, for the first time, highly collimated unidirectional microlasers. The breakthrough elliptical cavity enables a wide range of applications in photonics.

The new microlaser uses an elliptical resonator with a wavelength-sized notch (seen at top right) on the boundary to create unidirectional rays (bottom left).
Credit: Courtesy of the laboratory of Federico Capasso, Harvard School of Engineering and Applied Sciences (SEAS)

Utilizing a century-old phenomenon discovered in St. Paul's Cathedral, London, applied scientists at Harvard University have demonstrated, for the first time, highly collimated unidirectional microlasers.

The result of a collaboration with researchers from Hamamatsu Photonics in Hamamatsu City, Japan, and the Institute of Theoretical Physics of the University of Magdeburg, Germany, the advance has a wide range of new applications in photonics such as sensing and communications.

Published online this week in the Proceedings of the National Academy of Sciences, the research team took advantage of a concept in physics referred to as "whispering gallery modes."

Over a century ago, British scientist Lord Rayleigh wondered how two people standing on opposite sides of the dome in St. Paul's Cathedral could hear each other by whispering into the circular wall. He discovered that the sound skirts along the smooth surface of the wall with negligible attenuation due to scattering or absorption.

The optical analog of whispers in a dome are light rays confined to the perimeter of tiny circular disks by multiple reflections from the boundary as they circle around. Because attenuation is minimal within the smooth disk, these resonators have already been used to make some of the world's lowest-threshold lasers. Circular disks, however, have posed certain challenges.

"One of the crucial unsolved problems of these microlasers for practical applications has been that their emission is non-directional and their optical power output is negligible," said team leader Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at Harvard's School of Engineering and Applied Sciences (SEAS).

"Light gets trapped by these whispering gallery modes with little chance to escape except by a faint isotropic emission. Strategies to suitably deform the disks to solve this problem have yielded disappointing results," Capasso added.

By shaping the microlaser as an ellipse with a wavelength-size notch carved out from its edge, Capasso's team found that the cycling whispering gallery modes scatter efficiently off the notch and emerge as nearly parallel beams from the microlaser.

The prototypes are quantum cascade lasers emitting an optical power of 5 milliwatts at a wavelength of 10 microns. The microlaser performance is insensitive to the details of the notch, making this device design very robust.

"Our calculations show that the notched elliptical microlaser should have even better performance at the shorter wavelengths near 1 micron, typical of laser diodes used in optical communications, where the attenuation of whispering gallery modes is negligible," said coauthor Jan Wiersig of the Institute of Theoretical Physics of the University of Magdeburg.

"The successful realization of these simple-structured and robust microlasers through standard wafer-based fabrication makes small-volume directional light sources possible for many important applications such as photonic integrated circuits with high-density chip-scale integration, optical communications, medical/biological sensors, and lab-on-a-chip," said coauthor Masamichi Yamanishi, Research Fellow of Central Research Laboratories at Hamamatsu.

The team's other authors are postdoc Nanfang Yu, research associates Laurent Diehl and Christian Pflügl, all at SEAS; Qi Jie Wang and Changling Yan, formerly postdocs at SEAS and now with the Technological University in Singapore, and the Changchun University of Science and Technology in Changchun, China, respectively; graduate student Julia Unterhinninghofen of the Institute of Theoretical Physics at the University of Magdeburg; and researchers Tadataka Edamura and Hirofumi Kan of Hamamatsu Photonics.

The research was partially supported by the Air Force Office of Scientific Research. The Harvard authors also acknowledge the support of two Harvard-based centers, the National Science Foundation Nanoscale Science and Engineering Center (NSEC) and the Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Infrastructure Network (NNIN).


Story Source:

The above story is based on materials provided by Harvard University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Qi Jie Wang, Changling Yan, Nanfang Yu, Julia Unterhinninghofen, Jan Wiersig, Christian Pflügl, Laurent Diehl, Tadataka Edamura, Masamichi Yamanishi, Hirofumi Kan and Federico Capasso. Whispering-gallery mode resonators for highly unidirectional laser action. PNAS, December 13, 2010 DOI: 10.1073/pnas.1015386107

Cite This Page:

Harvard University. "Highly unidirectional 'whispering gallery' microlasers created." ScienceDaily. ScienceDaily, 13 December 2010. <www.sciencedaily.com/releases/2010/12/101213151415.htm>.
Harvard University. (2010, December 13). Highly unidirectional 'whispering gallery' microlasers created. ScienceDaily. Retrieved October 1, 2014 from www.sciencedaily.com/releases/2010/12/101213151415.htm
Harvard University. "Highly unidirectional 'whispering gallery' microlasers created." ScienceDaily. www.sciencedaily.com/releases/2010/12/101213151415.htm (accessed October 1, 2014).

Share This



More Matter & Energy News

Wednesday, October 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Japan Looks To Faster Future As Bullet Train Turns 50

Japan Looks To Faster Future As Bullet Train Turns 50

Newsy (Oct. 1, 2014) — Japan's bullet train turns 50 Wednesday. Here's a look at how it's changed over half a century — and the changes it's inspired globally. Video provided by Newsy
Powered by NewsLook.com
US Police Put Body Cameras to the Test

US Police Put Body Cameras to the Test

AFP (Oct. 1, 2014) — Police body cameras are gradually being rolled out across the US, with interest surging after the fatal police shooting in August of an unarmed black teenager. Duration: 02:18 Video provided by AFP
Powered by NewsLook.com
Raw: Japan Celebrates 'bullet Train' Anniversary

Raw: Japan Celebrates 'bullet Train' Anniversary

AP (Oct. 1, 2014) — A ceremony marking 50 years since Japan launched its Shinkansen bullet train was held on Wednesday in Tokyo. The latest model can travel from Tokyo to Osaka, a distance of 319 miles, in two hours and 25 minutes. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Robotic Hair Restoration

Robotic Hair Restoration

Ivanhoe (Oct. 1, 2014) — A new robotic procedure is changing the way we transplant hair. The ARTAS robot leaves no linear scarring and provides more natural results. Video provided by Ivanhoe
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins